class SM4Cipher:
    def __init__(self, key: bytes):
        if not len(key) == 16:
            raise ValueError("SM4 key must be length of 16. ")
        self._key_r = self._generate_key(key)
        self.block_size = 16

    def encrypt(self, plaintext: bytes):
        return self._do(plaintext, self._key_r)

    def decrypt(self, ciphertext: bytes):
        return self._do(ciphertext, self._key_r[::-1])

    def _do(self, text: bytes, key_r: list):
        text_ = [0 for _ in range(4)]
        # 将 128bit 转化成 4x32bit
        for i in range(4):
            text_[i] = int.from_bytes(text[4 * i:4 * i + 4], 'big')
        for i in range(32):
            box_in = text_[1] ^ text_[2] ^ text_[3] ^ key_r[i]
            box_out = self._s_box(box_in)
            temp = text_[0] ^ box_out ^ self._rot_left(box_out, 2) ^ self._rot_left(box_out, 10)
            temp = temp ^ self._rot_left(box_out, 18) ^ self._rot_left(box_out, 24)
            text_ = text_[1:] + [temp]
        text_ = text_[::-1]  # 结果逆序
        # 将 4x32bit 合并成 128bit
        result = bytearray()
        for i in range(4):
            result.extend(text_[i].to_bytes(4, 'big'))
        return bytes(result)

    def _generate_key(self, key: bytes):
        """密钥生成"""
        key_r, key_temp = [0 for _ in range(32)], [0 for _ in range(4)]
        FK = [0xa3b1bac6, 0x56aa3350, 0x677d9197, 0xb27022dc]
        CK = [0x00070e15, 0x1c232a31, 0x383f464d, 0x545b6269, 0x70777e85, 0x8c939aa1, 0xa8afb6bd, 0xc4cbd2d9,
              0xe0e7eef5, 0xfc030a11, 0x181f262d, 0x343b4249, 0x50575e65, 0x6c737a81, 0x888f969d, 0xa4abb2b9,
              0xc0c7ced5, 0xdce3eaf1, 0xf8ff060d, 0x141b2229, 0x30373e45, 0x4c535a61, 0x686f767d, 0x848b9299,
              0xa0a7aeb5, 0xbcc3cad1, 0xd8dfe6ed, 0xf4fb0209, 0x10171e25, 0x2c333a41, 0x484f565d, 0x646b7279]
        # 将 128bit 拆分成 4x32bit
        for i in range(4):
            temp = int.from_bytes(key[4 * i:4 * i + 4], 'big')
            key_temp[i] = temp ^ FK[i]
        # 循环生成轮密钥
        for i in range(32):
            box_in = key_temp[1] ^ key_temp[2] ^ key_temp[3] ^ CK[i]
            box_out = self._s_box(box_in)
            key_r[i] = key_temp[0] ^ box_out ^ self._rot_left(box_out, 13) ^ self._rot_left(box_out, 23)
            key_temp = key_temp[1:] + [key_r[i]]
        return key_r

    @staticmethod
    def _s_box(n: int):
        BOX = [0xD6, 0x90, 0xE9, 0xFE, 0xCC, 0xE1, 0x3D, 0xB7, 0x16, 0xB6, 0x14, 0xC2, 0x28, 0xFB, 0x2C, 0x05, 0x2B,
               0x67, 0x9A, 0x76, 0x2A, 0xBE, 0x04, 0xC3, 0xAA, 0x44, 0x13, 0x26, 0x49, 0x86, 0x06, 0x99, 0x9C, 0x42,
               0x50, 0xF4, 0x91, 0xEF, 0x98, 0x7A, 0x33, 0x54, 0x0B, 0x43, 0xED, 0xCF, 0xAC, 0x62, 0xE4, 0xB3, 0x1C,
               0xA9, 0xC9, 0x08, 0xE8, 0x95, 0x80, 0xDF, 0x94, 0xFA, 0x75, 0x8F, 0x3F, 0xA6, 0x47, 0x07, 0xA7, 0xFC,
               0xF3, 0x73, 0x17, 0xBA, 0x83, 0x59, 0x3C, 0x19, 0xE6, 0x85, 0x4F, 0xA8, 0x68, 0x6B, 0x81, 0xB2, 0x71,
               0x64, 0xDA, 0x8B, 0xF8, 0xEB, 0x0F, 0x4B, 0x70, 0x56, 0x9D, 0x35, 0x1E, 0x24, 0x0E, 0x5E, 0x63, 0x58,
               0xD1, 0xA2, 0x25, 0x22, 0x7C, 0x3B, 0x01, 0x21, 0x78, 0x87, 0xD4, 0x00, 0x46, 0x57, 0x9F, 0xD3, 0x27,
               0x52, 0x4C, 0x36, 0x02, 0xE7, 0xA0, 0xC4, 0xC8, 0x9E, 0xEA, 0xBF, 0x8A, 0xD2, 0x40, 0xC7, 0x38, 0xB5,
               0xA3, 0xF7, 0xF2, 0xCE, 0xF9, 0x61, 0x15, 0xA1, 0xE0, 0xAE, 0x5D, 0xA4, 0x9B, 0x34, 0x1A, 0x55, 0xAD,
               0x93, 0x32, 0x30, 0xF5, 0x8C, 0xB1, 0xE3, 0x1D, 0xF6, 0xE2, 0x2E, 0x82, 0x66, 0xCA, 0x60, 0xC0, 0x29,
               0x23, 0xAB, 0x0D, 0x53, 0x4E, 0x6F, 0xD5, 0xDB, 0x37, 0x45, 0xDE, 0xFD, 0x8E, 0x2F, 0x03, 0xFF, 0x6A,
               0x72, 0x6D, 0x6C, 0x5B, 0x51, 0x8D, 0x1B, 0xAF, 0x92, 0xBB, 0xDD, 0xBC, 0x7F, 0x11, 0xD9, 0x5C, 0x41,
               0x1F, 0x10, 0x5A, 0xD8, 0x0A, 0xC1, 0x31, 0x88, 0xA5, 0xCD, 0x7B, 0xBD, 0x2D, 0x74, 0xD0, 0x12, 0xB8,
               0xE5, 0xB4, 0xB0, 0x89, 0x69, 0x97, 0x4A, 0x0C, 0x96, 0x77, 0x7E, 0x65, 0xB9, 0xF1, 0x09, 0xC5, 0x6E,
               0xC6, 0x84, 0x18, 0xF0, 0x7D, 0xEC, 0x3A, 0xDC, 0x4D, 0x20, 0x79, 0xEE, 0x5F, 0x3E, 0xD7, 0xCB, 0x39,
               0x48]
        result = bytearray()
        # 将 32bit 拆分成 4x8bit，依次进行S盒变换
        for item in list(n.to_bytes(4, 'big')):
            result.append(BOX[item])
        return int.from_bytes(result, 'big')

    @staticmethod
    def _rot_left(n, m):
        """循环左移"""
        return ((n << m) | (n >> (32 - m))) & 0xFFFFFFFF


# filepath1 = 'e:\\mms\\plaintext.txt'
# filepath2 = 'e:\\mms\\cryptotext.txt'
# # key = bytes.fromhex('127382AB47BDC76ACD90FDB8ED78BF8D')
# key = bytes.fromhex('0123456789ABCDEFFEDCBA9876543210')
# sm4 = SM4Cipher(key)
# with open(filepath1) as fp1:
#         plain = fp1.read()
# fp2 = open(filepath2,'a+')
# for i in range(0, len(plain)-32, 32):
#     # plain = bytes.fromhex(plain[i:i+32])
#     fp2.write(sm4.encrypt(bytes.fromhex(plain[i:i+32])).hex())
# # print(i)
# fp2.write(sm4.encrypt(bytes.fromhex(plain[len(plain)-32:len(plain)])).hex())
# fp2.close()
